Method and apparatus for applying tire tread for a retread tire

ABSTRACT

An apparatus for retreading tires is disclosed. The apparatus has a rotatable hub for the mounting of a buffed tire casing. The apparatus also has a cushion gum applicator that is configured to stretch a length of cushion gum onto a tire casing. Further, the apparatus has a tread dispenser that is configured to automatically dispense a length of tire tread based on the circumference of at least one of the tire casing and the tire casing plus the cushion gum. Further still, the apparatus includes a tread applicator that is configured to stretch the length of tire tread onto the cushion gum. The entire apparatus including the cushion gum applicator, the tread dispenser, and the tread applicator are integrated into a single tire bench machine.

FIELD OF THE INVENTION

The invention relates generally to a method and apparatus for makingretreaded tires and particularly to a method of and apparatus in whichthe steps in making a retreaded tire are combined on a single integratedmachine.

BACKGROUND OF THE INVENTION

Retreaded tires are readily available and provide an economical way togain additional use out of tire casings after the original tread orretread has become worn. According to a conventional method ofretreading, sometimes referred to as cold process retreading, worn tiretread on a used tire is removed by a special buffing machine that grindsaway old tread and leaves a buffed surface to which a new layer of treadmay be bonded.

Removal of old tread from the tire casing provides a generally smoothtreadless surface about the circumference of the tire casing. The tirecasing may then be examined for injuries, which are skived and filledwith a repair gum. After completion of the skiving process, the buffedsurface may be sprayed with a tire cement that provides a tacky surfacefor application of bonding material and new tread. Next a layer ofcushion gum is applied to the back, i.e., the inside surface of a newlayer of tread, or alternatively, the layer of cushion gum is applieddirectly to the tacky surface on the tire casing. Conventionally, thecushion gum is a layer of uncured rubber material. The cushion gum andtread may be applied in combination about the circumference of the tirecasing to create a retreaded tire assembly ready for curing.Alternatively, a length of tire tread is wrapped around the tire casingwith the cushion gum already applied. The cushion gum forms the bondbetween the tread and the tire casing during curing.

Following assembly of the tire casing, cement, cushion gum and tread,the overall retreaded tire assembly is placed within a flexible rubberenvelope. An airtight seal is created between the envelope and the beadof the tire. The entire envelope tire assembly is placed within a curingchamber, and subjected to pressure and a raised temperature for aspecific period of time. The combination of pressure, temperature, andtime binds a layer of cushion gum to both the tire casing and the newtire tread.

The above-described method of cold process retreading is oftenaccomplished on a tire builder. Conventional tire builders include aspindle on which a tire is mounted and a spindle on which a roll of tirecushion gum is mounted for dispensing. Typically the cushion gum may bedispensed by hand as the tire is rotated to adhere the cushion gum tothe tire casing.

In certain applications, it may be advantageous to eliminate the spraycement completely. This may be particularly true in geographical areaswhere there is increased regulation of the use of chemicals within spraycement products. Further, use of spray cement can also add to the costof producing retreaded tires due to the product cost and equipment cost.Various solutions to enable a cementless process have been suggested,for example, extruding heated cushion gum directly to a tire casing.This process however, is costly due to equipment costs and isunnecessarily complex.

After the cushion gum has been applied, the circumference of the tirecasing with cushion gum is measured and an applicable length of tread ismeasured out, conventionally on a separate bench. The tire tread ismanually cut to length.

In all tire building systems once the cushion gum has been applied andthe tread has been cut to length, the tread must be applied to thecushion gum and casing. Due to errors in the cut length of the tiretread it may be desirable to stretch the tire tread around the perimeterof the tire casing and cushion gum in order to create an appropriatelysized splice.

Further, it is often desirable, for aesthetic and structural strengthpurposes, to match the tire tread design at each end of the tire treadlength so that where the two ends of the tire tread length match at thesplice, the repetitive pattern of the tire tread design is substantiallycontinuous. To create such a splice, it may be necessary to stretch thetire tread around the circumference of the tire casing and cushion gumbecause the tire tread length may have been cut to an extra shortenedlength in order to cause the matching of the tire tread design at thetwo ends of the tire tread.

Accordingly, there is a need for an integrated tread bench that combinesthe processes of cushion application, tread cutting and treadapplication into a single work bench machine while semi-automating theplurality of steps required to produce a finished retread tire prior tocuring. There is also a need for a cushion gum application process andapparatus that controls the stretch of the cushion gum duringapplication to the tire casing. Further, there is a need for a methodand apparatus for applying cushion gum to a tire casing that uses acementless application and stitching process. Further, there is a needfor a semi-automatic method and apparatus for cutting an appropriatelength of tire tread. Further still, there is a need for asemi-automatic method and apparatus of applying tire tread in acontrolled stretch to a casing with an applied cushion gum to produce atire with a predetermined range of splice size. Yet further still, thereis a need for a semi-automatic method and apparatus of cutting andapplying tire tread lengths such that the periodic tire tread design issubstantially continuous in the retread tire.

SUMMARY OF THE INVENTION

An exemplary embodiment of the invention relates to a tread applicationapparatus for use in applying a length of tire tread to a tire casing.The apparatus includes a rotatable hub for mounting a tire casing, thetire casing having a circumference. The apparatus also includes a trackconfigured to provide the length of tire tread to the casing, the lengthof tire tread having a first end and a second end. Further, theapparatus includes a variable force applicator configured to apply thelength of tire tread onto the casing.

Another exemplary embodiment of the invention relates to a treadapplication apparatus for use in applying a length of tire tread to atire casing having an applied cushion gum. The tread applicationapparatus includes a rotatable hub for mounting a tire casing, the tirecasing having a circumference. The tread application apparatus alsoincludes a track configured to provide the length of tire tread to thecushion gum, the length of tire tread having a first end and a secondend. Further, the tread application apparatus includes a variable forceapplicator configured to apply the length of tire tread onto the cushiongum.

Still another exemplary embodiment of the invention relates to a methodof applying a length of tire tread to a tire casing having a layer ofcushion gum applied thereto. The method includes mounting a tire casingon a hub, the hub being rotatable. The method also includes applying thelength of tire tread to the cushion gum. Further, the method includescontrolling the pressure applied to the tire tread during application.Further still, the method includes monitoring the distance needed to becovered by the tire tread and monitoring the length of tire tread notapplied to the cushion gum.

BRIEF DESCRIPTION OF THE DRAWINGS

The Invention will become more fully understood from the followingdetailed description, taken in conjunction with the accompanyingdrawings, wherein like reference numerals refer to like elements, inwhich:

FIG. 1 is a mechanical drawing of an integrated tire bench system;

FIG. 2 is a perspective view of an integrated tire bench system;

FIG. 3 is a partial elevation view of an integrated tire bench system;

FIG. 4 is a cross-sectional view of a tire casing in an application orstitching operation; and

FIG. 5 is a depiction of the kinematics of a cushion gum applicationprocess.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, an integrated tire bench 10 is depicted.Tire bench 10 is a semi-automated retread tire building apparatusconfigured to assemble retread tires. In an exemplary embodiment, tirebench 10 includes a rotatable hub 20 for mounting a tire casing thereon.In an exemplary embodiment, hub 20 may be a variable size hub thatincorporates an automated inflation system and is configured toaccommodate tires having different sizes (widths and radii).

Tread bench 10 includes an operator control panel 25 having a pluralityof buttons and gauges 26 to partially control and monitor operations oftread bench 10. Tread bench 10 also includes a cushion gum applicatorsystem 30. Cushion gum applicator system 30 includes a spindle 32 towhich may be mounted a roll of cushion gum 34 provided for dispensingonto a tire casing 22 mounted on hub 20.

Cushion applicator system 30 also includes a drive wheel 36 that isconfigured to engage the surface of a tire casing and is driven by therotation of tire casing 22. In an exemplary embodiment, drive wheel 36is coupled to spindle 32 a via a system of gears and/or belts 37, suchthat spindle 32 a rotates with a surface velocity that is proportionalto the surface velocity with which casing 22 is rotated by a drivesystem 23, rotating hub 20.

Further still, in an exemplary embodiment, tread bench 10 includes a setof applicator/stitcher wheels 40. Applicator/stitcher wheels 40 aremovable relative to one another and may be moved adjacent one another toform a single applicator/stitcher wheel. Applicator/stitcher wheels 40may be moved apart to perform stitching operations. Applicator/stitcherwheels 40 may also be moved in a direction substantially normal to thesurface of the tire casing to apply a variably controlled force to thesurface in contact with applicator/stitcher wheels 40.

A measurement wheel 50 is provided on a measurement arm 52. Measurementarm 52 is pivotable by actuation through a pneumatic cylinder 54 toengage a surface (either a tire casing, or cushion gum applied to a tirecasing). Measurement wheel 50 rotates, as a tire casing 22 is rotated onan axis 24. Measurement wheel 50 is coupled to an encoding device whichencodes the angular variation of measurement wheel 50 for communicationto a central processing unit or control unit. In combination, wheel 50with control unit yields appropriate measurement of wheel circumference.In alternative embodiments, other measurement devices may beincorporated into the design without departing from the spirit and scopeof the invention.

Tread bench 10 also includes a tread dispensing system 60. Referring nowto FIG. 3, tread dispensing system 60 includes a tread rollers 62 onwhich a roll of rubber tire tread 64 may be mounted. Tread dispensingsystem 60 also includes a set of drive rollers 66 which may be used topull tire tread 68 from roll 64 and push out a length of tire tread 79away from rollers 66. Tread dispensing system 60 also includes a knife70 for cutting a length of tire tread 79 from uncut tread 68. Furtherstill, tread dispensing system 60 includes a first clamp 72 and a secondclamp 74. First clamp 72 is configured to clamp tire tread 68 at or neara first end 76. Second clamp 74 is configured to clamp tire tread 68 ator near a second end 78, created by knife 70.

Tire bench 10 includes a curved track that may be a set of rollers 82mounted along curved track 80. Curved track 80 is configured as a curveto provide a desirable height for operator access at or near knife 70.Further, curved track 80 is configured to deliver tire tread section 79to the end of track 80 adjacent casing 22, for assembly thereon, withoutintroducing any substantial bending or stretching caused by abruptchanges in the path of travel of section 79 and further to facilitatethe movement of first clamp 72 and second clamp 74 along track 80.Curved track 80 is also appropriately curved to allow a desirable heightfor operator access near knife 70 while providing adequate height at theopposite end to accommodate tires of large size.

In an exemplary embodiment, first clamp 72 pulls tread section 79 alongtrack 80 to provide tread section 79 to contact casing 22. As treadsection 79 is applied to tire casing 22, second end 78 is at a knownlocation because clamp 74 includes an encoder (in communication with acentral processing unit or control unit) configured to track thelocation of end 78 relative to end 76 which is engaged with casing 22.Both clamps 72 and 74 have encoders incorporated therein to track thelocation of clamps 72 and 74 along track 80. In an exemplary embodiment,the encoders of clamps 72 and 74 are able to measure changes everymillimeter. However, encoders of clamps 72 and 74 are not limited toreceiving data every millimeter but may be configured to receiveinformation on larger or smaller scales. The measurement of changesevery millimeter provides a substantially continuous location signal toa central processing unit or control unit used to control theapplication process. However, it may be desirable to providesubstantially continuous monitoring with coarser or finer measurements.

In operation, an operator mounts a tire casing 22 to hub 20. Hub 20 maybe moved laterally, along the axis of rotation in order to center hub 20relative to a longitudinal center line of tread bench 10, whichcorresponds to the center line of cushion gum 34 and tire tread roll 64.Once the casing has been mounted, the casing is then inflated andcentered. Therefore, the first step for the operator after mounting andinflating casing 22 is to align the center line of tire casing 22 withthe center line of the cushion gum 34 and tire tread roll 64, which areautomatically aligned with the tread bench 10 centerline by a system ofclamps, guides, rollers, or other alignment devices. Next, measurementwheel 50 is brought into contact with the outer surface of casing 22.Tire casing 22 is rotated to provide a measurement of the circumferenceof casing 22. While casing 22 is rotated a full revolution, measurementwheel 50 encodes rotations of measurement wheel 50 which arecommunicated to a central processing unit or control unit where adetermination of the circumference of tire casing 22 is calculated. Fromthe measurement of the circumference of casing 22, a desired maximumangular velocity is determined, based on a desired value of thetangential velocity of points on the surface of casing 22 during cushiongum application.

In an exemplary embodiment it may be desirable to obtain a maximumtangential velocity of points on the surface of casing 22 during cushiongum application, for casings of various sizes, the maximum tangentialvelocity being constant across the range of sizes. To provide a constantmaximum velocity across the range of sizes requires knowledge of thesize (i.e., the circumference) of each casing. Alternatively, it may bedesirable to vary the tangential velocity based on size, or it may bedesirable to provide a constant angular velocity over the range ofsizes.

Next, drive roller 36 is brought into contact with the outer surface ofcasing 22. A length of cushion gum is dispensed from roll 34 and appliedto the surface of casing 22. Casing 22 is rotated and consequentiallyrotates both drive wheel 36 and spindle 32 causing the cushion gum tostretch and be applied to casing 22. To produce the controlled stretchof cushion gum 34, casing 22 is driven by the rotation of hub 20 throughdrive system 23. Drive wheel 36, which engages casing 22, is caused torotate and drive a system of gears and/or belts 37 thereby drivingspindle 32 a at a linear surface velocity based proportionally on thelinear surface velocity of casing 22. Gearing 37 is configured such thata linear velocity of cushion gum being dispensed from roll 34 is lessthan the tangential velocity of points on the perimeter of casing 22.Therefore, the differential velocity, that is the tangential velocity ofa point on the perimeter of casing 22 minus the linear velocity ofcushion gum leaving roll 34, is non-negative. The differential velocitytherefore produces a stretching of cushion gum 34 as it is being appliedto the exterior of casing 22.

Referring now to FIG. 5, to fully illustrate the cushion gum stretchingprocess, roll 34 is depicted having an angular velocity ω₂. Cushion gum34 is shown being applied to casing 22, casing 22 having an angularvelocity ω₁. To cause stretching of cushion gum 34, a point 90 on thesurface of casing 22 has a velocity V1, a point 91 on the cushion gum,being dispensed from the roll 34, has a velocity V2. Because ω₁ and ω₂are geared to provide different V2 and V1, where V1 is greater than V2,a differential velocity ΔV=V1-V2, that is non-negative is created.Therefore, due to the differential velocity, the cushion gum isnecessarily stretched.

As depicted in FIG. 4, casing 22 has a curved crown section 27. Crown 27is substantially the surface to which cushion gum 34 is applied. In anexemplary embodiment, cushion gum 34 has a polyethylene protective layer35 adhered thereto, to prevent adhesion to other layers of cushion gumwhile rolled and to prevent adhesion to application rollers 40 duringapplication. The controlled stretching of cushion gum 34, by thedifferential velocity introduced by gears 37, provides improvedconformity of cushion gum 34 to the contoured crown 27 of casing 22. Theimproved conformity provides uniform adhesion and contact of cushion gum34 to crown 27 causing the cushion gum edge to substantially contactcasing 22 wrinkle-free and further reduces the need for providing extrastrips of cushion gum along shoulders 21 of crown 27 (i.e., cushion gumstripping).

Because measurement of the circumference of casing 22 was provided bymeasurement wheel 50, the known length of cushion gum 34 is dispensed tofully encompass the perimeter of casing 22.

After cushion gum 34 has been applied to casing 22, rollers 40 are movedto engage and provide a force onto cushion gum 34. Casing 22 is rotatedwhile rollers 40 provide a force, in a direction indicated by arrow 38in FIG. 4, onto cushion gum 34. In an exemplary embodiment, wheels 40begin in the middle of crown 27 and, during subsequent rotations, wheels40 are moved towards shoulders 21 of crown 27 in the directionsindicated by arrows 41. This operation, often referred to as stitching,provides desirable adherence of cushion gum 34 to the surface of casing22 (crown 27 and shoulders 21), while aiding in removing any trapped airpockets between cushion gum 34 and casing 22. After the stitchingoperation is completed, a measurement of the circumference of tirecasing 22 plus cushion gum layer 34 is taken by measurement wheel 50 ascasing 22 is rotated. Polyethylene layer 35 is then removed.

Based on the measured circumference of tire casing 22 with cushion gumlayer 34 adhered thereto, a desired length of tire tread may bedetermined. In an exemplary embodiment, the determined length isdispensed from tread roll 64, as depicted in FIG. 3. The tread 68 isdispensed by drive rollers 66 beneath a retracted cutter 70 and throughclamps 72 and 74 to a stop 75 which is extended upwardly above track 80.When end 76 engages stop 75, clamp 72 is selectively commanded to engagetread section 79 (adjacent end 76) to carry tread 79 along withmovements of clamp 72. Stop 75 is then lowered and based on a determinedlength, roller 66 drives tread 68 pushing end 76 along track 80 and pastclamp 74, while clamp 72 cooperatively propels tread end 76 along track80. When an approximate desired length has been reached, based onaforementioned circumferential measure, drive 66 stops deploying tread68 and clamp 72 stops propelling tread end 76.

In an exemplary embodiment, an operator may, once an approximate lengthof tread 68 has been deployed, make minor adjustments to a location ofcut 78 in tread 68. It may be desirable for an operator to match theperiodically repeating tread design of end 76 with the tread design atend 78. Matching the designs of ends 76 and 78 provide a preferredaesthetic appeal and structural strength, at the splice region in acompleted retread tire by providing a continuously repeating treaddesign substantially unbroken by the splice. (In an alternativeembodiment, the process of selecting the appropriate splice location,based on the tread design may be carried out by image processing deviceswhich control the deployment of tread 68, location of end 78, andmatching of designs on ends 76 and 78). Once the targeted location ofend 78 is determined by an operator, or alternatively by automatedmethods, cutter 70 is used to cut section 79 away from tread 68remaining behind knife 70 and on roll 64. Further, clamp 74 is clampedin a position adjacent end 78.

After end 78 has been created by cutter 70, clamp 72, which moves alongtrack 80, pulls section 79 along track 80. End 76 is then put in contactwith cushion gum 34 on casing 22 and application wheels 40 are loweredto engage end 76 of tread 79. An encoder is used to determine thelocation of end 76 relative to casing 22. The location of end 76 issubstantially continuously communicated to a central processing unit orcontrol unit. Casing 22 is then rotated while applicator wheels 40provide a variably controlled pressure to tread 79. The applied pressureby wheels 40 provide adherence of tread 79 to cushion gum 34 and extendthe overall length of tread 79 due to the force being exerted byapplicator wheels 40 and the associated Poisson effect.

As casing 22 is rotated, the location of clamp 74 and hence end 78 oftread 79 is monitored. Further, because the location of edge 76 and thecircumference of casing 22 with cushion gum 34 applied thereto is known,the circumferential distance yet to be covered by tread 79, may bededuced. By comparing the remaining circumferential distance to becovered and the amount of tread not yet applied, an appropriate forcemay be commanded to be applied by applicator wheels 40, to provide theappropriate amount of stretching and ultimately to match ends 76 and 78with a gap having a gap length falling within a predetermined range.

Once the tread 79 has been applied, the operator may manually providefinishing operations to the splice area, or alternatively devices may beadded to automatically finish the splice area. Finally, tire casing 22,may be removed from hub 20, and placed in a pressurized flexibleenvelope for curing.

Those who have skill in the art will recognize that the presentinvention is applicable with many different hardware configurations,software architectures, sensing and communication devices, andmechanical configurations.

While the detailed drawings, specific examples, and particularformulations given describe exemplary embodiments, they serve thepurpose of illustration only. The materials and configurations shown anddescribed may differ depending on the chosen performance characteristicsand physical characteristics of tires and tire treads. For example, thelayout and configuration of the tread bench may differ. The systemsshown and described are not limited to the precise details andconditions disclosed. Furthermore, other substitutions, modifications,changes, and omissions may be made in the design, operating conditions,and arrangement of the exemplary embodiments without departing from thespirit of the invention as expressed in the appended claims.

What is claimed is:
 1. A method of applying a length of tire treadhaving a first end and a second end to a tire casing having a layer ofcushion gum applied thereto, the tire casing and the cushion gum havinga circumference, the method comprising: mounting the tire casing on ahub, the hub being rotatable; measuring, automatically, thecircumference of the tire casing and cushion gum; dispensing along atrack the length of tire tread based on the measured circumference ofthe casing and the cushion gum, the length of tire tread having a firstend; adjusting the length of tire tread along the track with respect toa cutter so that, after being cut, the first and a second end of thetread will provide a substantially continuous tread design when broughttogether on said tire casing; cutting said length of tire tread todefine the second end; connecting an encoder to the tire tread at adetermined distance from the second end; moving the length of tire treadalong the track to provide the length of tire tread to the casing;applying the length of tire tread to the circumference of the tirecasing and cushion gum; monitoring the circumferential distance of thecasing and cushion gum not covered by the tire tread; monitoring thelength of tire tread not applied to the casing and cushion gum bymonitoring the location of the second end of the tire tread via theencoder; and controlling the pressure applied to the tire tread duringapplication, the pressure applied to the tread based on thecircumferential distance of the casing and cushion gum not covered bythe tire tread and the length of tire tread not applied to the casingand cushion gum, so that the first and second ends of the tread willprovide a continuous tread design when applied.
 2. The method of claim1, further comprising: moving the hub to align the tire casing with thetread.
 3. The method of claim 1, further comprising: stitching the tiretread to the cushion gum.
 4. The method of claim 1, further comprising:rotating the hub to pull the length of tire tread onto the cushion gum.5. The method of claim 1, further comprising: engaging the tire treadwith an application wheel configured to apply pressure to the tiretread.
 6. The method of claim 1 wherein the length of tire tread has aperiodically repeating tread design, and the length of the tire tread isdefined by matching the tread design at the first and second endsthereof to provide a splice region, the splice region defined by theends when applied to the tire casing, that has a substantially unbroken,continuously repeating tread design.
 7. The method of claim 1 wherein inthe controlling step, the circumferential distance of the casing andcushion gum not covered by the tire tread and the length of tire treadnot applied to the casing and cushion gum are compared to command anappropriate pressure applied to the tread to apply the first and secondends of the length of tire tread onto the casing such that the endsdefine a gap, the gap having a gap length falling within a predeterminedrange.
 8. The method of claim 6 wherein in the controlling step, thecircumferential distance of the casing not covered by the tire tread andthe length of tire tread not applied to the cushion gum are compared tocommand an appropriate pressure applied to the tread to apply the firstand second ends of the length of tire tread onto the casing such thatthe ends define a gap, the gap having a gap length falling within apredetermined range.
 9. The method of claim 1 wherein monitoring thecircumferential distance of the casing not covered by the tire treadoccurs substantially continuously.
 10. The method of claim 1 whereinmonitoring the length of the tread not applied to the casing and cushiongum occurs substantially continuously.
 11. The method of claim 10wherein monitoring the length of the tread not applied to the casing andcushion gum occurs substantially continuously.
 12. The method of claim1, wherein an encoder adapted to determine the location of the first endof the tire tread relative to the casing during the application of thetire tread to the casing is provided to monitor the circumferentialdistance of the casing and cushion gum not covered by the tire treadstep.
 13. The method of claim 1, wherein moving the length of tire treadalong the track occurs without introducing any substantial bending orstretching of the tire tread.